Centrifuge apparatus

ABSTRACT

A HEAVY PHASE MATERIAL, SEPARATED FROM A LIGHT PHASE MATERIAL AND ACCUMULATED ON THE PERIHPERAL WALL OF A CENTRIFUGE BOWL, IS REMOVED FROM THE BOWL BY A SKIMMER IN RESPONSE TO SENSING ACTION OF A DETECTOR. THE LATTER INCLUDS AN OVERFLOW CONDUIT EXTENDING INWARDLY FROM AN OPENING IN THE BOWL WALL TO THE MAXIMUM DESIRED LEVEL OF THE HEAVY PHASE MATERIAL. TO CONDUIT CONDUCTS A SAMPLE OF THE MATERIAL AT SUCH LEVEL TO A GRAVIMETRIC DEVICE WHICH SENSES AN INCREASE IN SPECIFIC GRAVITY ABOVE THAT OF THE LIGHT PHASE MATERIAL, AS WOULD BE OCCASIONED BY ITS CONTAMINATION WITH HEAVY PHASE MATERIAL. THE DEVICE INDICATES THAT HEAVY PHASE MATERIAL HAS ACCULATED TO THE MAXIMUM DESIRED LEVEL AND RESPONDS BY ACTUATING A SKIMMER FOR REMOVING THE HEAVY PHASE MATERIAL FROM THE BOWL.

Feb. 2, 1971 c. E. TRUMP CENTRIFUGE APPARATUS Filed July 8, 1968 9\ IL WM 1 1 L IN. w w 9 w E2;

vm Emnihm INVI'INTUR. C E. Trump ATTORNEY 3,560,125 CENTRIFUGE APPARATUS Charles Edward Trump, Bedford, N.Y., assignor to Pennwalt Corporation, a corporation of Pennsylvania Filed July 8, 1968, Ser. No. 743,075 Int. Cl. B04b 11/00 U.S. Cl. 233-19 6 Claims ABSTRACT OF THE DISCLOSURE A heavy phase material, separated from a light phase material and accumulated on the peripheral wall of a centrifuge bowl, is removed from the bowl by a skimmer in response to sensing action of a detector. The latter includes an overflow conduit extending inwardly from an opening in the bowl wall to the maximum desired level of the heavy phase material. The conduit conducts a sample of the material at such level to a gravimetric device which senses an increase in specific gravity above that of the light phase material, as would be occasioned by its contamination with heavy phase material. The device indicates that heavy phase material has accumulated to the maximum desired level and responds by actuating a skimmer for removing the heavy phase material from the bowl.

This invention relates to centrifuge apparatus having a bowl in which light and heavy phase materials are separated from one another and wherein the heavy phase material is discharged from the bowl automatically in response to a signal from specific gravity measuring device located outside the bowl.

The invention is applied to the separation of a light phase material, usually a liquid, from a heavy phase material which may be either a solid material or another liquid of specific gravity greater than the light phase. Therefore, although the invention will be described herein as applied to the separation of solids or sludge from a mixture with a light phase liquid, it is to be understood that it is applicable where two liquids of different specific gravity are separated.

In proir art apparatus, feed is delivered to the bowl and clear eflluent is discharged over a lip at one end of the bowl. Accumulated solids often form a cake against the peripheral wall of the centrifuge bowl. After a predeter' mined period of time, based on experience, which approximates the period required for sludge to build up to the maximum desired level, feed is shut off by the timer and the sludge is discharged. Sludge discharge may be accomplished by a skimmer which first penetrates the inner layer of efl'luent and discharges the same while the bowl is still rotating; and then as the skimmer reaches the sludge-effluent interface, the operator manually diverts the discharge to waste so as not to comingle the sludge with the efliuent already collected. Thereafter, with the sludge removed from the bowl to the extent practicable, the skimmer is returned to its inward rest position and feed to the bowl is resumed.

The foregoing manual or semi-automatic process of the prior art is disadvantageous because the concentration of sludge in the feed is variable and it is therefore not possible to predict with accuracy the time period required to accumulate the maximum desired amount of sludge in the bowl. Thus, if the solids accumulation period is too short the operation of the machine will be inefficient, and if the same period is too long, sludge will contaminate the effluent. In the interest of efliciency, it is also desirable to provide apparatus which discharges solids automatically so that an operator will not be required.

According to the present invention, there is provided inwardly of the bowl an overflow conduit extending United States Patent radially inwardly from an opening in the bowl wall to the maximum desired level of the sludge. With this arrangement, a sample of clear eflluent will flow through the conduit and out the bowl with low sludge levels. But when the sludge is accumulated to above the maximum desired level, the conduit will discharge a mixture of effluent and sludge to a control tank outwardly of the bowl. It is to be understood, however, that there is also a primary effluent discharge in the form of an overflow lip at one end of the bowl, so that the overflow conduit serves only to extract a small sample of the material in the bowl at the inner end of the overflow conduit. It is contemplated that the control tank will overflow its contents to either the eflluent collecting tank, the sludge collecting tank, or the feed supply tank, depending upon the particular process and the composition of the feed. As a novel feature of the invention, a gravimetric type swich is installed in the control tank, or otherwise operatively associated with the sample control liquid, for the purpose of sensing the increased specific gravity of the control material which results when solids are first discharged from the bowl with the eflluent. When this condition occurs, the gravimetric switch can automatically terminate introduction of feed to the centrifuge bowl and also initiate the discharge of solids from the bowl.

Various objects, features and advantages of the invention will appear more fully from the detailed description which follows, taken in connection with the accompanying single figure drawing, in which there is shown a partly schematic and partly sectional view of a centrifuge and associated apparatus embodying the invention.

As shown in the drawing, the centrifuge is generally designated by the numeral 10. The latter includes a base 12 with a plurality of upright standards 14, only one of which is shown, together with means for suspending a centrifuge housing 18 from the standards. At the lower end of the housing 18 is a bearing 20 which is mounted with a centrifuge bowl 22 on a shaft, the latter having a lower end extending downwardly through the bearing for reception in a pulley 24 driven by motor 26 by suitable belt means.

Preferably the centrifuge bowl 22 is a cylindrical shell including an imperforate bottom wall 28 and a peripheral wall 30, also preferably imperforate-but not necessarily so. The upper end wall is also imperforate, with an inner annular edge thereof providing a discharge overflow lip 32. For some applications radial vanes extending in axial direction may be provided interiorly of the bowl 22, but these are omitted from the present illustration for the sake of brevity and clearness.

Feed slurry is introduced to the bowl 22 through a stationary feed tube 38, mounted in spaced and coaxial relationship with the upper end of the bowl. The tube 38 is provided with a normally closed solenoid-operated valve 39 which opens when electrically energized. At the top of a bowl hub is provided a feed-receiving cup 40 which rotates with the bowl and receives feed for distribution downwardly and outwardly toward the bottom of the bowl through a plurality of feed conduits 42, each having outlet openings at their remote ends.

Between the bowl housing 18 and the peripheral wall '30 of the bowl 22, is an annular space divided into upper and lower portions 41 and 43 by a horizontal annular partition 44. Preferably, the outer end of the partition 44 is rigidly secured to the housing 18; and the inner end thereof establishes a seal with the peripheral wall 30 of the bowl 22. With this arrangement, the upper annular space 41 receives clarified eflluent flowing over the overflow lip 32.

Further provided is an eflluent outlet conduit 45 connected to the upper end of the centrifuge bowl housing 18 for communication with the upper annular space 41. The conduit 45 connects to an effluent tank 46 for receiving and collecting clarified effluent from the centrifuge bowl.

For removing the sludge in the cyclical operation, the centrifuge is provided with a skimming device 50. This device includes a tube 51 of substantially J shape which presents an open mouth 52 facing the direction of rotation of the bowl 22. This skimmer tube 51 is mounted on the housing 18 in a plurality of bosses 54 in which it is longitudinally movable to position the open mouth 52 in various radial positions between the peripheral bowl wall 30 and locations inwardly thereof. Skimrning devices are well known in the art, and therefore it will suffice to say that as the skimmer is moved outwardly, deeper into the rotating bowl, a combination of the velocity of the liquid passing into the stationary skimmer tube 51 and the centrifugal pressure head of the material being removed, causes the material to be pumped into and through the skimmer device 50.

Means for driving the skimmer device 50 are provided in the form of a traversing mechanism indicated generally by the numeral 56. Such means may comprise a pair of pneumatic piston-cylinder assemblies which are well known as suitable to drive the skimmer tube 51 alternately forward and back. The arrangement is such that, at one extreme of movement, the skimmer tube 51 is disposed with its mouth 52 inwardly of the lip 32 and therefore out of contact with the material in the centrifuge bowl 22. At the other end of its travel the skimmer mouth 52 has small clearance, e.g. /1 inch, between its structure and the peripheral wall 30 so that it is capable of removing virtually all of the sludge accumulated within the bowl. Limit switches or valves may be provided for cooperation with the skimming device 50 at opposite ends of travel, together with reversing valves or switches for effecting reverse movement of the driving means.

Referring now more particularly to the inventive subject matter, the control device includes one or more control tubes 60 leading from an opening in the peripheral wall 30 in which it is sealed, securely mounted as by a threaded connection, and oriented in radial and horizontal direction to extend inwardly of the bowl 22. The inner end of each tube 60 may be threaded and fitted, as shown, with a nozzle 62. It is contemplated that nozzles 62 of various lengths and orifice size will be provided with the apparatus so that the total radial extent of the tube 60 and also its flow area can be adjusted.

As will appear more fully, adjustment of the radial inward extent of tube 60 is to the level of the maximum desired accumulated sludge within the bowl 22, as indicated by the broken line designated A. Since such maximum desired accumulation can vary from application to application, this means of adjustment is believed to be economical, convenient, and effective. With this arrangement, the tubes 60 conduct a sample of material, taken from the inner end of the nozzle 62, and discharge it into the lower annular space 43. This sample material, which may be also termed control liquid, is conducted to a control tank 64 by means of a conduit 66 connected between the centrifuge housing 18 and the tank 64 for communication with the lower annular space 43 and the interior of the tank 64.

At the bottom of the tank 64 is a discharge valve 68 which is normally closed but which may be opened to discharge accumulated sludge. At the top of the tank 64 is an overflow pipe 70 for discharging control liquid, from which solids may have settled, either to the effluent collecting tank 46, to a feed supply tank (not shown), or to a sludge receiving tank (not shown).

Connected between the opposite ends of the conduit 66 is a detecting device generally indicated by the numeral 72. Such device is commercially available from the Fisher Governor Company and, as described in their Bulletin F4C, as on pages 32 and 33, their type 2500259B control is responsive to changes in specific gravity of liquid flowing therethrough. The device 72 may include an elongated tubular member 74 having an inlet 76 midway along its length to provide for divided flow toward opposite outlet ends 78 thereof. Parallel pipes 80 are connected to the respective outlet ends 78 and each are provided with manually operable flow valves 82 which are adjustable to effect balanced outlet flow through the pipes 80. A downstream T connection 84 to the pipes 80, merges the divided flows for continued conduction through the balance of the conduit 66 to the tank 64. Disposed in the tubular member 74 is a float or displacer 85 which is displaced to an extent related to the specific gravity of the flowing material conducted thereby and transmits small changes in specific gravity by mechanical means to a control box 86. The control box 86 is suitably energized by a source of electrical power (not shown) and responds to a predetermined displacement of the float 85 by transmitting an electrical signal through line 87 to the solenoidoperated valve 39 and the traversing mechanism 56.

From the foregoing it can be seen that, in operation, when accumulated sludge or heavy phase material is acculated above the level A, it will be discharged at least in part with the light phase effluent through the control tube 60 for passage through the lower annular space 43, thence through the conduit 66 and the tubular member 74 where an increase in specific gravity is detected. Flow continues on to the tank 64, with efiluent overflowing through the pipe 70 and solids settling to the bottom of the tank 64. The control box 86 responds to the detected increase in specific gravity by effecting closure of the valve 39 to interrupt the inflow of feed to the centrifuge bowl 22. The control 86 also effects outward traversing movement of the skimmer device 50 in order to empty the bowl 22 of both effluent and accumulated solids.

Optionally, valve 68 can be a normally closed solenoidactuated valve which is connected by a suitable lead to control 86 to be opened when energized for automatically draining the contents of tank 64.

In order to segregate the clarified effluent from the accumulated solids removed by the skimming device 50, a lug or protuberance 90 is rigidly or adjustably mounted on the skimming device between the bosses 54. Also provided, is a limit switch 92 which is actuated by the lug 90 in either direction of travel of the skimming device. The limit switch 92 is connected, as shown, to a solenoidoperated diversional valve 94 arranged so that when the limit switch 92 is tripped in one direciton, as when the skimmer is driven outward toward the bowl wall, the solenoid-operated diversional valve 94 is thrown to the waste position to discharge heavy phase material as the mouth 52 of the skimmer reaches the line A. By return of the skimmer when the lug 90 engages the limit switch 92, the solenoid-operated diversional valve 94 is operated in the reverse direction to divert the flow of discharging material to the eflluent position. With this arrangement, effective segregation of clarified effiuent and accumulated solids is effected, since the light phase material is discharged to one discharge line and the heavy phase is discharged to another discharge line. The light phase eflluent thus discharged can be conducted to the tank 46.

Further provided is a limit switch 95 which is actuated by the traversing mechanism as it returns with the skimming device 50 to the reset or innermost position. Actua tion of the limit switch 95 resets the valve 39 and the control 86 for the next cycle. In addition, if valve 68 is a solenoid-actuated valve, according to the option described above, the limit switch 95 also serves to close the drain valve 68 by deenergizing its solenoid.

It is also optional, in some applications, to eliminate the tank 64 and discharge the sample material from the end of conduit 66 after flowing through the tubular member 74 and the pipes 82.

It is to be understood that, although the invention has been shown and described as having a particular kind of detecting device 72, the invention can be practiced with other kinds of devices which are responsive to changes in specific gravity of the control material. For example, a

float type gravimetric switch can be disposed in the tank 64. Likewise, various other changes and modifications can be made to the illustrated arrangement without departing from the broad concept of the invention.

What is claimed is:

1. In centrifuge apparatus including a rotatably mounted centrifuge bowl having an annular inwardly extending liquid overflow lip formed about the rotational axis at at least one end, means for feeding to the bowl a mixture of at least two materials wherein the first material thereof has a higher specific gravity than the second material therof and whereby said .first material builds up against the peripheral wall of the bowl, means for discharging an accumulation of said first material from the bowl, and that improvement comprising means for indicating when said first material has accumulated in the bowl to a predetermined level inward of the peripheral wall and outward of said lip, and means responsive to indication by said indicating means for initiating said means for discharging said first material from the bowl, said indicating means including a tubular passageway extending through the peripheral wall of the bowl inwardly of the bowl to said predetermined level for conducting material out of the bowl, means for receiving the material conducted out of the bowl by said passageway, and means operatively associated with said receiving means for detecting an increase in specific gravity of the material in said receiving means above the specific gravity of said second material for indicating to said initiating means that the material in said receiving means includes at least some of said first material together with said second material, whereby said second material is automatically discharged by said discharging means from said bowl when the accumulation of said first material in said bowl reaches said predetermined level.

2. Centrifuge apparatus according to claim 1 further including valve means for interrupting the operation of said feeding means in response to an indication by said indicating means.

a. Centrifuge apparatus according to claim 1 wherein 6 said tubular passageway includes a removable nozzle on the inner end thereof.

4. Centrifuge apparatus according to claim. 1 wherein the indicating means is a float member displaced to an extent related to the specific gravity of the material contacted thereby, and an electrical device responsive to a predetermined displacement of said float member for transmitting a signal to initiating means.

5. Centrifuge apparatus according to claim 4 further including means for collect-ing said second material outside said bowl, and a housing for said bowl disposed about said rotational axis and defining an annular space about said bowl, a partition dividing said annular space into upper and lower portions, one of said portions of said annular space communicating between said passageway and said receiving means, and the other of said portions of said annular space communicating between the overflow lip and said collecting means.

6. Centrifuge apparatus according to claim 1 wherein said peripheral wall of said bowl is of imperforate construction, the buildup of said first material against the peripheral wall taking place beneath an inwardly disposed layer of said second mateiral, and wherein a major portion of said second material overflows said lip as said 25 first material is accumulating in said bowl.

References Cited UNITED STATES PATENTS 2,532,792 12/1950 Svensjo. 3,011,647 12/1961 Elsken.

3,052,401 9/1962 Thylefors. 3,167,509 1/1965 Steinacker, 3,261,546 7/1966 Gruver.

ROBERT w. JENKINS, Primary Examiner US. 01. X.R, 2s3 14, 22 

